Defrost apparatus of refrigerator

ABSTRACT

The present invention discloses a defrost apparatus of a refrigerator which can defrost an evaporator by a defrost heater, when moisture of the ambient air of the evaporator is frozen on the surface of the evaporator. The defrost apparatus of the refrigerator includes a pair of evaporators and a pair of defrost heaters to selectively defrost the pair of evaporators. A path varying means for guiding air flow is installed near the pair of evaporators. The air is not supplied to the defrosted evaporator, for performing the defrosting operation. The air is supplied to the non-defrosted evaporator, for performing the cooling operation. As a result, the defrosting operation is efficiently performed, and the temperature does not sharply increase in freezing and refrigerating chambers, so that the food can be maintained fresh for an extended period of time.

TECHNICAL FIELD

The present invention relates to a defrost apparatus of a refrigeratorwhich can perform a defrosting operation by using a defrost heater andcontrolling inflow of the ambient air, when moisture of the ambient airof an evaporator is frozen on the surface of the evaporator.

BACKGROUND ART

In general, refrigerators are classified into a direct cooling typerefrigerator and an indirect cooling type refrigerator according to acooling method. In the direct cooling type refrigerator, evaporators areinstalled on inner walls of a freezing chamber and a refrigeratingchamber. The cool air generated around the evaporators is naturallyconvected to cool the freezing chamber and the refrigerating chamber. Inthe indirect cooling type refrigerator, an evaporator is installed ininner walls of a freezing chamber, and a fan is installed on a cool aircirculation path. The cool air generated around the evaporator isforcibly sent by the fan to cool the freezing chamber and therefrigerating chamber.

In the indirect cooling type refrigerator, when the fan is operated, theair of the freezing chamber and the refrigerating chamber directlypasses through the evaporator, and then is circulated. Therefore,moisture of the air of the freezing chamber and the refrigeratingchamber is frozen on the surface of the evaporator, therebydeteriorating the heat exchange performance. In order to solve the aboveproblem, an electric heater is installed at the lower portion of theevaporator, for directly defrosting the surface of the evaporator.

FIG. 1 is a side-sectional view illustrating a conventional defrostapparatus of a refrigerator, and FIG. 2 is a graph showing a temperatureinside the refrigerator in the operation of the conventional defrostapparatus of the refrigerator.

Referring to FIG. 1, in the conventional refrigerator, a freezingchamber F and a refrigerating chamber R are installed at upper and lowerportions of a front surface of a refrigerator main body 2 a and 2 b, afreezing chamber door 4 a and a refrigerating chamber door 4 b areinstalled to be opened and closed on the front surface of therefrigerator main body 2 a and 2 b, an evaporator 10 is installed on thespace formed on the inner wall of the freezing chamber F, a freezingcycle including the evaporator 10 is installed at one side of therefrigerator main body 2 a and 2 b, and a ventilation fan 12 and a motor14 are installed at the upper portion of the evaporator 10, for sendingthe cool air to the freezing chamber F and the refrigerating chamber R.

Here, the refrigerator main body 2 a and 2 b includes an insulationmaterial (not shown) between an outer casing 2 a and an inner casing 2b. A compressor 6, a condenser 8 and a capillary tube (not shown)connected to the evaporator 10 through refrigerant tubes are built in amechanical chamber formed at the lower portion of the refrigerator mainbody 2 a and 2 b. The evaporator 10 is built in the inner casing 2 b ofthe freezing chamber F, and a drain tube (not shown) for guidingcondensed water formed on the surface of the evaporator 10 and a drainfan (not shown) for collecting the condensed water are installed at thelower portion of the condenser 8.

A cool air circulation path is formed inside the inner casing 2 b of therefrigerating chamber R and a plurality of cool air distribution holes 2h are formed in the inner casing 2 b of the refrigerating chamber R, sothat the cool air heat-exchanged in the evaporator 10 can be circulatedin the refrigerating chamber R as well as the freezing chamber F.

A temperature sensor (not shown) and a defrost heater 20 are installedat one side of the evaporator 10. Even if moisture of the air passingthrough the evaporator 10 is frozen on the surface of the evaporator 10,frost formation is sensed by the temperature sensor and the evaporator10 is defrosted by the defrost heater 20.

The components such as the compressor 6 and the motor 14 are connectedto and controlled by a control unit (not shown).

Accordingly, when the control unit operates the compressor 6 and themotor 14, the refrigerants are circulated through the compressor 6, thecondenser 8, the capillary tube and the evaporator 10, and exchange heatwith the ambient air of the evaporator 10, thereby generating the coolair. When the ventilation fan 12 is rotated, the cool air is sent to thefreezing chamber F and the refrigerating chamber R in order to performthe freezing and refrigerating operations.

On the other hand, when the control unit senses frost formation on thesurface of the evaporator 10 by the temperature sensor, the control unitstops the operations of the compressor 6 and the ventilation fan 12, andoperates the defrost heater 20 to defrost the evaporator 10. When thesurface of the evaporator 10 is defrosted, the control unit resumes thefreezing and refrigerating operations.

However, the conventional defrost apparatus of the refrigerator includesthe defrost heater 20 adjacently to the evaporator 10 so as to defrostthe surface of the evaporator 10. As illustrated in FIG. 2, while thedefrost heater 20 is operated, the air heated along the opened cool aircirculation path is circulated to cause a heat shock sharply increasingthe temperature of the freezing chamber F. It is thus difficult tomaintain the food fresh.

To solve the foregoing problem, as disclosed under Japanese Laid-OpenPatent Application 9-33157, an evaporator is partitioned off by a centerpartition plate, and thermostats and heaters corresponding to each areaof the evaporator are installed at the upper and lower portions thereof.The heaters are individually operated to partially defrost theevaporator.

However, in the conventional defrost apparatus, when the two heaters areinstalled in each area of the evaporator, even if the partition isinstalled to partition the two heaters and each area of the evaporator,the air paths are linked at the top and bottom ends of the evaporator.Accordingly, the air passing through the defrosted portion of theevaporator and the air passing through the non-defrosted portion of theevaporator are mixed and supplied to the freezing chamber F, to increasethe temperature of the freezing chamber F.

In addition, in the conventional defrost apparatus, one evaporatorformed by installing a plurality of fins on one refrigerant tube ispartitioned off by the partition, and the defrost heaters are installedin each area of the evaporator. Even if heat is applied to one sideevaporator of the partition, heat is transmitted to the other sideevaporator through the refrigerant tube and the plurality of fins,thereby performing the defrosting operation at a time. The heattransmitted to the whole evaporator heats the ambient air and suppliesthe heated air to the freezing chamber F, thereby increasing thetemperature of the freezing chamber F. As a result, the food cannot bemaintained fresh for an extended period of time.

DISCLOSURE OF THE INVENTION

The present invention is achieved to solve the above problems. An objectof the present invention is to provide a defrost apparatus of arefrigerator which can prevent temperature rise in a whole freezingchamber by locally defrosting two evaporators individually installed onthe inner wall of the freezing chamber by heaters corresponding to theevaporators.

Another object of the present invention is to provide a defrostapparatus of a refrigerator which can prevent temperature rise in afreezing chamber by selectively forming air guiding paths, even if twoevaporators installed on the inner wall of the freezing chamber aredefrosted by heaters corresponding to the evaporators.

In order to achieve the above-described objects of the invention, thereis provided a defrost apparatus of a refrigerator, including: arefrigerator main body in which a freezing chamber and a refrigeratingchamber are formed, cool air circulation holes being formed on apartition wall for separating the freezing chamber from therefrigerating chamber; a freezing cycle including first and secondevaporators installed on a cool air circulation path on the inner wallof the freezing chamber, for cooling the air by the heat exchangeoperation with refrigerants, and a compressor, a condenser and expansionmeans built in one side of the refrigerator main body to be connected tothe first and second evaporators, for circulating the refrigerants; aventilation device installed at one side of the first and secondevaporators, for sending the cool air from the first and secondevaporators to the freezing chamber; temperature sensors installed inthe first and second evaporators, for sensing temperature variations ofthe first and second evaporators, respectively; first and second defrostheaters installed in the first and second evaporators and controlledaccording to the sensing values of the temperature sensors, fordefrosting the first and second evaporators, respectively; a refrigerantdistributing means for wholly or selectively distributing therefrigerants to the first and second evaporators; a path varying meansinstalled between the first and second evaporators, for controllinginflow of the cool air to the first and second evaporators; and acontrol unit for controlling the operations of the ventilation device,the first and second defrost heaters, the refrigerant distributing meansand the path varying means according to the sensing values of thetemperature sensors.

Preferably, the expansion means are first and second capillary tubesconnected to the first and second evaporators, respectively, fordecompressing the refrigerants, and the refrigerant distributing meansis a 3-way valve installed between the condenser and the first andsecond capillary tubes.

Preferably, the path varying means includes a partition wall installedon the cool air circulation path, for partitioning off the first andsecond evaporators, and first and second dampers rotatably installed onthe front and rear ends of the partition wall, for selectivelycontrolling inflow of the cool air to the first and second evaporators.

Preferably, the control unit operates one of the first and seconddefrost heaters or stops the first and second defrost heaters accordingto the sensing values of the temperature sensors, and continuouslyoperates the ventilation device.

More preferably, when the first defrost heater is operated, the controlunit controls the 3-way valve to supply the refrigerants to the secondcapillary tube and the second evaporator, and also controls the firstand second dampers to supply the cool air to the second evaporator.Conversely, when the second defrost heater is operated, the control unitcontrols the 3-way valve to supply the refrigerants to the firstcapillary tube and the first evaporator, and also controls the first andsecond dampers to supply the cool air to the first evaporator.

Preferably, when the first and second defrost heaters are not operated,the control unit controls the 3-way valve to supply the refrigerants tothe first and second capillary tubes and the first and secondevaporators, and also controls the first and second dampers to supplythe cool air to the first and second evaporators.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become better understood with reference tothe accompanying drawings which are given only by way of illustrationand thus are not limitative of the present invention, wherein;

FIG. 1 is a side-sectional view illustrating a conventional defrostapparatus of a refrigerator;

FIG. 2 is a graph showing a temperature inside the refrigerator in theoperation of the conventional defrost apparatus of the refrigerator;

FIG. 3 is a partially-cut front view illustrating a refrigerator mainbody to which a defrost apparatus is applied in accordance with thepresent invention;

FIG. 4 is a structure view illustrating a freezing cycle of therefrigerator using the defrost apparatus in accordance with the presentinvention;

FIG. 5 is a block diagram illustrating control flow of the defrostapparatus of the refrigerator in accordance with the present invention;and

FIGS. 6 a and 6 b are structure views illustrating refrigerant flow andair flow in the defrosting operation in the freezing cycle of therefrigerator using the defrost apparatus in accordance with the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

A defrost apparatus of a refrigerator in accordance with the presentinvention will now be described in detail with reference to theaccompanying drawings.

Referring to FIGS. 3 and 5, in the refrigerator, a freezing chamber Fand a refrigerating chamber R are formed at both sides of a refrigeratormain body 52 having its front surface opened, a cool air circulationpath A is formed on the inner wall of the freezing chamber F, first andsecond evaporators 68 a and 68 b and a ventilation device are installedon the cool air circulation path A of the freezing chamber F, and thefreezing cycle except the first and second evaporators 68 a and 68 b isinstalled in a space formed at one side of the freezing chamber F and/orthe refrigerating chamber R. When the freezing cycle and the ventilationdevice are driven, the cool air is supplied to the freezing chamber Fand the refrigerating chamber R. First and second temperature sensors 69a and 69 b and first and second defrost heaters 72 a and 72 b areinstalled at the upper and lower portions of the first and secondevaporators 68 a and 68 b in order to rapidly sense and defrost thefrost-formed surfaces of the first and second evaporators 68 a and 68 b.A path varying means is further installed to guide flow of the ambientair of the first and second evaporators 68 a and 68 b by the operationsof the first and second defrost heaters 72 a and 72 b. A control unit 90controls the operations of the components including the path varyingmeans.

A partition wall 54 is formed long in the up/down longitudinal directionin the refrigerator main body 52 having its front surface opened. Thefreezing chamber F and the refrigerating chamber R are formed side byside at both sides of the partition wall 54. The first and secondevaporators 68 a and 68 b are installed side by side on the cool aircirculation path A on the inner wall of the freezing chamber F, and coolair discharge holes 52 h for discharging the cool air generated aroundthe first and second evaporators 68 a and 68 b are formed thereon.

Here, an inflow path 54 a for supplying the cool air of the freezingchamber F to the refrigerating chamber R and a recovering path 54 b forrecovering the cool air of the refrigerating chamber R to the cool aircirculation path A of the freezing chamber F are formed on the partitionwall 54. Preferably, the inflow path 54 a and the recovering path 54 bare formed at the upper and lower portions of the partition wall 54,respectively, so that the cool air supplied to the refrigerating chamberR through the inflow path 54 a can be circulated in the refrigeratingchamber R and recovered.

The freezing cycle includes a compressor 62, a condenser 64, expansionmeans 66 a and 66 b and the first and second evaporators 68 a and 68 bconnected to each other through refrigerant tubes, so that therefrigerants can be compressed, condensed, evaporated and expandedduring the circulation to perform the cooling operation. The expansionmeans 66 a and 66 b can be comprised of first and second electronicexpansion valves for controlling decompression of refrigerants, but arecomprised of generally-used first and second capillary tubes 66 a and 66b. The first and second capillary tubes 66 a and 66 b are connected tothe first and second evaporators 68 a and 68 b, respectively.

The decompression degree of the first and second capillary tubes 66 aand 66 b is determined in proportion to the capacity of the first andsecond evaporators 68 a and 68 b. The diameter and length of the firstand second capillary tubes 66 a and 66 b are determined according to thedecompression degree. Here, when the decompression degree of the firstand second capillary tubes 66 a and 66 b increases, the diameter thereofis narrowed and the length thereof is lengthened.

A refrigerant distributing means for wholly or selectively distributingthe refrigerants to the first and second evaporators 68 a and 68 b bycontrolling the inflow direction of the refrigerants is installedbetween the condenser 64 and the first and second capillary tubes 66 aand 66 b. Preferably, a 3-way valve 65 is used as the refrigerantdistributing means. The 3-way valve 65 is installed at the branch pointof the refrigerant tubes between the condenser 64 and the first andsecond capillary tubes 66 a and 66 b.

The ventilation device is fixedly installed on the cool air circulationpath A to be positioned over the first and second evaporators 68 a and68 b. The ventilation device includes a ventilation fan 70 and a motorto send the cool air. When the ventilation fan 70 is operated, the coolair passing through the first and second evaporators 68 a and 68 b isforcibly sent and discharged through the cool air discharge holes 52 h.

The ventilation device can be comprised of a pair of ventilation fansand motors installed at the upper portions of the first and secondevaporators 68 a and 68 b, respectively.

The first and second temperature sensors 69 a and 69 b are installed atthe upper portions of the first and second evaporators 68 a and 68 b,for sensing the temperature of the surfaces of the first and secondevaporators 68 a and 68 b, respectively. The temperature and thetemperature variations are inputted to the control unit 90. The controlunit 90 controls the operations of each component.

Here, the sensing values of the first and second temperature sensors 69a and 69 b are inputted to the control unit 90. The control unit 90decides whether frost has been formed on the first and secondevaporators 68 a and 68 b according to the sensing value variations ofthe first and second temperature sensors 69 a and 69 b and therefrigerant supply to the first and second evaporators 68 a and 68 b.Even if the refrigerants are supplied to the first and secondevaporators 68 a and 68 b, if the sensing values of the first and secondtemperature sensors 69 a and 69 b are over a predetermined temperature,the control unit 90 decides that frost has been formed on the first andsecond evaporators 68 a and 68 b.

The first and second defrost heaters 72 a and 72 b are electric heatersinstalled at the lower portions of the first and second evaporators 68 aand 68 b for defrosting the surfaces of the first and second evaporators68 a and 68 b, respectively. The operations of the first and seconddefrost heaters 72 a and 72 b are controlled by the control unit 90according to the sensing values from the first and second temperaturesensors 69 a and 69 b.

The first and second defrost heaters 72 a and 72 b are not operated atthe same time but selectively operated. Preferably, the capacity of thefirst and second defrost heaters 72 a and 72 b is determined inproportion to the capacity of the first and second evaporators 68 a and68 b.

The path varying means includes a partition wall 82 for partitioning offthe first and second evaporators 68 a and 68 b side by side on the coolair circulation path A, and first and second dampers 84 a and 84 brotatably installed at the front and rear ends of the partition wall 82,for selectively controlling inflow of the cool air to the first andsecond evaporators 68 a and 68 b. The operations of the first and seconddampers 84 a and 84 b are also controlled by the control unit 90.

More components can be used to control the operations of the first andsecond dampers 84 a and 84 b by the control unit 90, but detailedexplanations thereof are omitted.

In the freezing and refrigerating operations, the control unit 90 sensesthe temperature of the freezing chamber F and the temperature of therefrigerating chamber R, and controls the operations of each component.However, in the defrosting operation, the control unit 90 controls theoperations of the first and second defrost heaters 72 a and 72 b, thefirst and second dampers 84 a and 84 b and the 3-way valve 65 accordingto the temperature values of the first and second temperature sensors 69a and 69 b.

In the freezing and refrigerating operations, the control unit 90 whollyopens the 3-way valve 65 and operates the compressor 62 and theventilation fan 70, so that the refrigerants can pass through thecompressor 62, the condenser 64, the first and second capillary tubes 66a and 66 b and the first and second evaporators 68 a and 68 b, and thatthe cool air generated by the heat exchange operation around the firstand second evaporators 68 a and 68 b can be supplied to the freezingchamber F and the refrigerating chamber R.

Preferably, the first and second dampers 84 a and 84 b are positioned inthe neutral position, so that the air can flow through the first andsecond evaporators 68 a and 68 b to maximize the heat exchange area.

On the other hand, in the defrosting operation, the control unit 90decides whether the first and second evaporators 68 a and 68 b have beendefrosted according to the measured temperature values of the first andsecond temperature sensors 69 a and 69 b. In a state where theventilation fan 70 is continuously operated, the first and secondevaporators 68 a and 68 b are sequentially defrosted one by one, whichwill now be explained in detail.

The operation of the defrost apparatus of the refrigerator in accordancewith the present invention will now be described in detail.

When the control unit 90 senses frost formation on the surface of thefirst evaporator 68 a according to the measured temperature values ofthe first and second temperature sensors 69 a and 69 b, as shown in FIG.6 a, the control unit 90 operates the first defrost heater 72 a,controls the 3-way valve 65 to supply the refrigerants to the secondcapillary tube 66 b and the second evaporator 68 b, controls the firstand second dampers 84 a and 84 b to intercept air flow to the firstevaporator 68 a and open air flow to the second evaporator 68 b, andcontinuously operates the ventilation fan 70.

Accordingly, when the first defrost heater 72 a is operated, the surfaceof the first evaporator 68 a is defrosted. The refrigerants arecirculated through the compressor 62, the condenser 64, the secondcapillary tube 66 b and the second evaporator 68 b, thereby cooling theambient air of the second evaporator 68 b. When the ventilation fan 70is operated, the air is supplied merely to the second evaporator 68 b,and thus the cool air around the second evaporator 68 b is re-suppliedto and circulated in the freezing chamber F. Conversely, the warm airaround the first evaporator 68 a is not directly supplied to thefreezing chamber F.

On the other hand, when the control unit 90 senses frost formation onthe surface of the second evaporator 68 b according to the measuredtemperature values of the first and second temperature sensors 69 a and69 b, as shown in FIG. 6 b, the control unit 90 operates the seconddefrost heater 72 b, controls the 3-way valve 65 to supply therefrigerants to the first capillary tube 66 a and the first evaporator68 a, controls the first and second dampers 84 a and 84 b to interceptair flow to the second evaporator 68 b and open air flow to the firstevaporator 68 a, and continuously operates the ventilation fan 70.

Therefore, when the second defrost heater 72 b is operated, the surfaceof the second evaporator 68 b is defrosted. The refrigerants arecirculated through the compressor 62, the condenser 64, the firstcapillary tube 66 a and the first evaporator 68 a, thereby cooling theambient air of the first evaporator 68 a. When the ventilation fan 70 isoperated, the air is supplied merely to the first evaporator 68 a, andthus the cool air around the first evaporator 68 a is re-supplied to andcirculated in the freezing chamber F. Conversely, the warm air aroundthe second evaporator 68 b is not directly supplied to the freezingchamber F.

When the control unit 90 senses frost formation on the surfaces of thefirst and second evaporators 68 a and 68 b at the same time according tothe measured temperature values of the first and second temperaturesensors 69 a and 69 b, the control unit 90 sequentially defrosts thefirst and second evaporators 68 a and 68 b in the same manner.

Although the preferred embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these preferred embodiments but various changes andmodifications can be made by one skilled in the art within the spiritand scope of the present invention as hereinafter claimed.

1. A defrost apparatus of a refrigerator, comprising: a refrigeratormain body in which a freezing chamber and a refrigerating chamber areformed, cool air circulation holes being formed on a partition wall forseparating the freezing chamber from the refrigerating chamber; afreezing cycle including first and second evaporators installed on acool air circulation path on the inner wall of the freezing chamber, forcooling the air by the heat exchange operation with refrigerants, and acompressor, a condenser and expansion means built in one side of therefrigerator main body to be connected to the first and secondevaporators, for circulating the refrigerants; a ventilation deviceinstalled at one side of the first and second evaporators, for sendingthe cool air from the first and second evaporators to the freezingchamber; temperature sensors installed in the first and secondevaporators, for sensing temperature variations of the first and secondevaporators, respectively; first and second defrost heaters installed inthe first and second evaporators and controlled according to the sensingvalues of the temperature sensors, for defrosting the first and secondevaporators, respectively; a refrigerant distributing means for whollyor selectively distributing the refrigerants to the first and secondevaporators; a path varying means installed between the first and secondevaporators, for controlling inflow of the cool air to the first andsecond evaporators; and a control unit for controlling the operations ofthe ventilation device, the first and second defrost heaters, therefrigerant distributing means and the path varying means according tothe sensing values of the temperature sensors.
 2. The defrost apparatusof claim 1, wherein the expansion means are first and second capillarytubes connected to the first and second evaporators, respectively, fordecompressing the refrigerants, and the refrigerant distributing meansis a 3-way valve installed between the condenser and the first andsecond capillary tubes.
 3. The defrost apparatus of claim 2, wherein thepath varying means comprises a partition wall installed on the cool aircirculation path, for partitioning off the first and second evaporators,and first and second dampers rotatably installed on the front and rearends of the partition wall, for selectively controlling inflow of thecool air to the first and second evaporators.
 4. The defrost apparatusof claim 3, wherein the control unit operates one of the first andsecond defrost heaters or stops the first and second defrost heatersaccording to the sensing values of the temperature sensors, andcontinuously operates the ventilation device.
 5. The defrost apparatusof claim 4, wherein, when the first defrost heater is operated, thecontrol unit controls the 3-way valve to supply the refrigerants to thesecond capillary tube and the second evaporator, and also controls thefirst and second dampers to supply the cool air to the secondevaporator.
 6. The defrost apparatus of claim 4, wherein, when thesecond defrost heater is operated, the control unit controls the 3-wayvalve to supply the refrigerants to the first capillary tube and thefirst evaporator, and also controls the first and second dampers tosupply the cool air to the first evaporator.
 7. The defrost apparatus ofclaim 4, wherein, when the first and second defrost heaters are notoperated, the control unit controls the 3-way valve to supply therefrigerants to the first and second capillary tubes and the first andsecond evaporators, and also controls the first and second dampers tosupply the cool air to the first and second evaporators.
 8. The defrostapparatus of claim 5, wherein, when the second defrost heater isoperated, the control unit controls the 3-way valve to supply therefrigerants to the first capillary tube and the first evaporator, andalso controls the first and second dampers to supply the cool air to thefirst evaporator.
 9. The defrost apparatus of claim 5, wherein, when thefirst and second defrost heaters are not operated, the control unitcontrols the 3-way valve to supply the refrigerants to the first andsecond capillary tubes and the first and second evaporators, and alsocontrols the first and second dampers to supply the cool air to thefirst and second evaporators.
 10. The defrost apparatus of claim 6,wherein, when the first and second defrost heaters are not operated, thecontrol unit controls the 3-way valve to supply the refrigerants to thefirst and second capillary tubes and the first and second evaporators,and also controls the first and second dampers to supply the cool air tothe first and second evaporators.